[0001] This invention relates to an improved lance pipe which is used for blasting oxygen
into molten steel, raising temperature of the melt and/or pre-treating the melt in
steel making furnace, ladle and tundish, or which is used for working such as melting
down of non-molten materials in the melting process of steel and as cutting of steel
scraps.
[0002] As steel lance pipes which are used for the oxygen blasting into molten steel, the
raising of temperature of the melt, and/or the pre-treating of the melt or which are
used for working such as the melting-down of non-molten materials, which is incidentally
carried out in the melting period, and as the cutting of steel scraps there have been
conventionally used one which is covered with refractories at the outer surface of
the steel pipe to decrease the wear caused by the melt loss when in use, one which
is covered with metal wire and/or refractory fiber with stud to reinforce the pipe
thereby preventing the release of the refractory coating, and a so-called calorized
one in which the surface of steel pipe is provided with an oxidation resistant aluminium-impregnated
layer.
[0003] However, a considerable number of equipments and steps are needed for carrying out
above working and treatments, and even in simple refractory coating treatment there
is such a disadvantage that to avoid the release of the coated layer the steel pipe
is covered with refractory after it is welded with a reinforcing stud as described
above, and further the content of the refractory composition itself is made complicated.
[0004] The present invention provides a lance pipe which have settled the above hard points
and prevents the refractory layer from releasing with a very simplified treatment.
That is, the lance pipe according to the invention is characterized in that it is
provided with a refractory coating layer which is in contact with -a steel pipe provided
with a knurling.
[0005] The "knurling" referred to herein is defined in JIS BO 106 to mean "to make knurling
nicks with a knurling tool" and it belongs to a rolled working. Further, the knurling
nicks made to the steel pipe can be optionally taken whether reticulate or stripe-patterned,
according to the shape of the working surface of the die called knurling tool, but
to sufficiently achieve the object of the invention an intersecting reticulate form
of said knurling nicks is more preferable than a stripe pattern in which the knurling
nicks are restricted in one direction. Furthermore, said working is extremely easy
and suitable for mass production.
[0006] Then the advantageous characteristic of knurling is that metal chips accompanied
by the working are not produced since the knurling belongs to a rolled working i.e.
a plastic working field. Accordingly the mass of the steel pipe is not decreased after
working so that the strength possessed by the steel pipe as base material is not impaired
at all thereby presenting a great merit when such steel pipe is used as a lance pipe.
It is conventionally well known to make streaks on the working surface by cutting
so as to avoid a release of unshaped refractory, but it is disadvantageous because
a separate consideration must be given to make up for the deterioration of the material,
which may be caused by the decrease of mass due to the generation of chips.
[0007] In carrying out the present invention the unshaped refractory coating layer can be
applied to any refractory composition usually used for lance pipe. In addition, it
is possible to handle similarly, as unshaped refractory coating layer, even ceramic
layer, cermet layer or one which forms a flame spray coating layer.
[0008] Thus it is capable of handling said layers similarly as unshaped refractory coating
layers being in contact with steel pipe applied with knurling.
[0009] According to the lance pipe worked with an unshaped refractory coating layer being
in contact with the steel pipe applied with knurling, an increase of the surface area
in the contact surface stabilizes the contact at room temperature, and at the same
time the difference between the expansion and the contraction, which occur between
the steel pipe and the coating layer, being accompanied by temperature rising and
cooling in operation, is dispersed not to cause a release.
[0010] The accompanying drawing is a perspective view showing an Example of the invention.
[0011] A JIS 15A steel pipe 1 of 5.5 m long applied with knurling nicks 2 of reticulation
having 0.4 mm depth and 0.8 mm pitch was coated at its surface with an unshaped cermet
refractory 3 consisting of 50% by weight of Fe, 45% by weight of Aℓ
2O
3 and 5% by weight of ZrSi0
4, added with 40% by weight of water glass. Said lance pipe was used for blasting oxygen
into molten carbon steel in a 5 ton arc furnace under the conditions of oxygen pressures
in the range 4-6 kg/cm
2 and melt temperatures in the range 1,620-1,630°C, but during the period of cooling
the lance pipe to room temperature in the atmosphere after the oxygen blasting any
release of the coated layer was not noticed. On the other hand, a lance pipe using
a steel pipe without knurling was subject to a comparative test under the same conditions
caused a release of the coating before it was cooled to room temperature so that it
needed repair for re-use. Further, it took only 40 seconds per lance pipe for the
knurling whereby the knurling working was very easy.
